Spinach and Sweet Potato Stuffed Mushrooms

As you know, I am trying to stick to whole, intact grains as much as possible. So, I couldn't make my traditional Spinach Stuffed Mushrooms since they have bread crumbs in them. This is a new twist made with sweet potatoes and walnuts instead.  They were so savory and delish!

12 large button mushrooms, stems removed and saved
1/4 red onion, chopped finely
1/4 cup walnuts
2 cups baby spinach
1 sweet potato, baked and cooled
1/2 t. dried rosemary
1/4 t. dried thyme
salt and pepper to taste
veggie broth

In a skillet, cook chopped onions until tender and translucent. While onions are cooking, add veggie broth if they stick to the pan.
While onions are cooking, process walnuts in food processor until finely ground.
Add in the mushroom stems, 2 of the mushrooms, and the baby spinach into the food processor and pulse until everything is in tiny pieces.
Place mixture into skillet with onions, add 1/4 cup veggie broth and seasonings and cook until the broth cooks out. Turn off the heat.
Add the sweet potato into the mixture and combine well.
Preheat oven to 375 degrees F.
Stuff mushrooms with the mixture and place in 13x9 baking dish.
Bake for about 30 minutes uncovered or until the mushrooms are tender.

Before baking